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Full-Text Articles in Physics

Examination Of The Relationship Between The Parameters Of Barkhausen Effect Model And Microstructure Of Magnetic Materials, Chester C.H. Lo, S. J. Lee, L. C. Kerdus, David C. Jiles May 2002

Examination Of The Relationship Between The Parameters Of Barkhausen Effect Model And Microstructure Of Magnetic Materials, Chester C.H. Lo, S. J. Lee, L. C. Kerdus, David C. Jiles

Center for Nondestructive Evaluation Publications

A relationship between the parameters of a hysteretic-stochastic process model of the Barkhausen effect (BE) and the microstructural features of a series of ferritic/pearlitic steel samples has been identified. The root-mean-square values and pulse height distributions of the experimental and modeled BE signals showed similar dependence on the pearlite content. The correlation length parameter ξ of the model, which represents the range of interaction of domain walls with pinning sites, was found to obey ξ=AVfDf+BVpDp where Vf(Vp)and Df(Dp) are the volume fraction and grain size of ferrite (pearlite).


Monitoring Fatigue Damage In Materials Using Magnetic Measurement Techniques, Chester C.H. Lo, F. Tang, Y. Shi, David C. Jiles, S. B. Biner Apr 1999

Monitoring Fatigue Damage In Materials Using Magnetic Measurement Techniques, Chester C.H. Lo, F. Tang, Y. Shi, David C. Jiles, S. B. Biner

Center for Nondestructive Evaluation Publications

Measurements of hysteresis and Barkhausen effect (BE) have been made on 0.1 wt % C Fe–C alloys subjected to strain-controlled fatigue at various strain amplitudes. A relationship between the fatigue lifetime and strain amplitude was observed. The hysteresis properties of the samples cycled at different strain amplitudes were found to vary systematically with expended fatigue life. These properties showed significant changes in the initial and final stages of fatigue, while between these stages they remained stabilized. In the stable stage the remanence was found to decrease, whereas the coercivity increased with increasing strain amplitude. Variations in BE signal during ...


Finite Element Analysis Of The Influence Of A Fatigue Crack On Magnetic Properties Of Steel, Y. Shi, David C. Jiles Jun 1998

Finite Element Analysis Of The Influence Of A Fatigue Crack On Magnetic Properties Of Steel, Y. Shi, David C. Jiles

Center for Nondestructive Evaluation Publications

Fatigue can affect the magnetic properties of materials due to microstructural changes. Previous investigations have shown that several structure sensitive magnetic properties, such as coercivityHc and remanenceBr, changed systematically as a result of fatigue. When approaching failure the accumulated changes in microstructure resulted in the occurrence of fatigue cracks and the magnetic properties showed dramatic changes which mainly resulted from the geometrical changes in samples due to the cracks. It was found that the remanenceBr followed the changes in stress, while the coercivityHc sometimes showed different trends. In this article the influence of the size and the position of a ...


Barkhausen Effect In Steels And Its Dependence On Surface Condition, Anthony P. Parakka, David C. Jiles, H. Gupta, M. Zang Apr 1997

Barkhausen Effect In Steels And Its Dependence On Surface Condition, Anthony P. Parakka, David C. Jiles, H. Gupta, M. Zang

Center for Nondestructive Evaluation Publications

Micromagnetic Barkhausen signals from magnetic materials originate from the discontinuous changes in magnetization under the action of a changing applied magnetic field.Barkhausen emissions that are detected by a sense coil come predominantly from a surface layer. In iron based materials this layer is about 500 μm thick. The Barkhausen signal is affected by changes in material microstructure and the presence of residual stress, since these affect the dynamics of domain wall motion. The selective attenuation of high frequency components of the Barkhausen signal due to eddy currents in electrically conducting materials is used to evaluate changes in material condition ...


Effects Of Surface Condition On Barkhausen Emissions From Steel, Anthony P. Parakka, David C. Jiles, H. Gupta, S. Jalics Apr 1996

Effects Of Surface Condition On Barkhausen Emissions From Steel, Anthony P. Parakka, David C. Jiles, H. Gupta, S. Jalics

Center for Nondestructive Evaluation Publications

Temperature changes during mechanical processing such as grinding of steel parts can cause phase changes in the microstructure. Thermal shock during the process can give rise to localized surface residual stress. The net result can be reduced wear resistance and fatigue life leading to early failure during service. Effective methods for the detection of such damage are necessary. Barkhausen emissions, which arise from discontinuous motion of domain walls, are sensitive to microstructual changes that affect domain dynamics. Detected Barkhausen signals are predominantly from a surface layer about 200 μm thick, those from deeper being attenuated due to eddy currents. An ...


Monitoring Neutron Embrittlement In Nuclear Pressure Vessel Steels Using Micromagnetic Barkhausen Emissions, Levent B. Sipahi, Madhav Rao Govindaraju, David C. Jiles May 1994

Monitoring Neutron Embrittlement In Nuclear Pressure Vessel Steels Using Micromagnetic Barkhausen Emissions, Levent B. Sipahi, Madhav Rao Govindaraju, David C. Jiles

Center for Nondestructive Evaluation Publications

In nuclear power plants, neutron embrittlement of pressure vessel steels has been one of the main concerns. The use of micromagnetic Barkhausen emissions is a promising method to monitor the variations in microstructural and subsurface stress states due to their influence on these emissions. Measurements of these emissions can reveal neutron irradiationdegradation in nuclear power plant components. Samples which were irradiated at differentneutron fluences and annealed at different temperatures were obtained from three reactor surveillance programs. The results of different neutron fluences and annealing procedures showed noticeable fractional changes in the magnetic Barkhausen effect signal parameter, ΔMBE/MBE, and in ...


A Model For Hysteretic Magnetic Properties Under The Application Of Noncoaxial Stress And Field, Martin J. Sablik, S. W. Rubin, L. A. Riley, David C. Jiles, David A. Kaminski, S. B. Biner Jul 1993

A Model For Hysteretic Magnetic Properties Under The Application Of Noncoaxial Stress And Field, Martin J. Sablik, S. W. Rubin, L. A. Riley, David C. Jiles, David A. Kaminski, S. B. Biner

Center for Nondestructive Evaluation Publications

Although descriptions of the effect of stress on spontaneous magnetization within a single domain already exist, there remains no adequate mathematical model for the effects of noncoaxial magnetic field and stress on bulk magnetization in a multidomained specimen. This article addresses the problem and provides a phenomenological theory that applies to the case of bulk isotropic materials. The magnetomechanical hysteresis model of Sablik and Jiles is thus extended to treat magnetic properties in the case of noncoaxial stress and magnetic field in an isotropic, polycrystalline medium. In the modeling, noncollinearity between magnetization and magnetic field is taken into account. The ...